1. Field of the Invention
The present invention relates to a method of magnetic resonance analysis employing cylindrical coordinates and a catheter antenna and related apparatus and, more specifically, it relates to such magnetic resonance imaging wherein alternating use of the catheter antenna and the body coil means as the source of the RF pulses facilitates obtaining high resolution images.
2. Description of the Prior Art
The advantageous use of non-invasive and non-destructive test procedures has long been known in both medicine and industrial applications. In respect of medical uses wherein it is desirable to limit a patient's exposure to potentially damaging x-ray radiation, it has been known to accomplish imaging objectives through the use of other non-invasive imaging procedures, such as, for example, ultrasound imaging and magnetic resonance imaging. See, for example, U.S. Pat. Nos. 4,766,381; 5,099,208; 5,352,979; and 5,512,825.
In a general sense, magnetic resonance imaging involves providing bursts of radio frequency (RF) energy to a region of interest of a specimen positioned in a main magnetic field in order to induce responsive emission of magnetic radiation from the hydrogen nuclei or other nuclei. The emitted signal may be detected in such a manner as to provide information as to the intensity of the response and the spatial origin of the nuclei emitting the responsive magnetic signal. In general, the imaging may be performed in a slice or plane, or multiple planes, or three-dimensional volume with information corresponding to the responsively emitted magnetic radiation being delivered to a computer which stores the information in the form of numbers corresponding to the intensity of the signal. The computer may establish a pixel value as by employing Fourier Transformations which convert the signal amplitude as a function of time to signal amplitude as a function of frequency. The signals may be stored in the computer and may be delivered with or without enhancement to a video screen display, such as a cathode-ray tube, for example, wherein the image created by the computer output will be presented through regions of contrasting black and white which vary in intensity or color presentations which vary in hue and intensity.
Obtaining ultra-high resolution in existing systems has been difficult. With conventional methods, microscopic or near-microscopic resolution can be achieved using high strength gradients with very short rise times. However, these gradients are very expensive and the nerve stimulation threshold imposes restrictions on maximum gradient strength.